Clown Goby Death, Ideas?

[shrimpinator123]

So, my clown goby (Gobiodon atrangulatus) in my 10 gal died. Not sure really what happened. He was acting normal, eating, did not look stressed, and was ultimately seemingly perfectly happy. Then, he just hit the dust. Checked the water, current parameters are:

Specific Gravity: 1.025
Ammonia: 0 ppm
Nitrite: 0ppm
Nitrate: 15 ppm

Other inhabitants include:
Yellow Watchmen Goby/Pistol Shrimp Pair
Peppermint Shrimp
1 turbo snails
3 hermit crabs
5 cerith snails

Everybody else seems fine, no weird behavior. Anybody have any ideas?

 

[shrimpinator123]

Forgot to mention that the only thing added to the tank was a HOB filter that was rated for 30-45 gallons, and that the PH has been steady since the tank was set up at 8.3.

 

[Uncle99]

Hermit crabs have been known to sneak up on bottom dwellers

 

[Cliving1]

Was he a new addition? If so, how did you acclimate.

 

[shrimpinator123]

Nope, he has been in their since the tank cycled (2 months) . Ordered him off LA and used their bag acclimation method. I do not think this could be hermit crabs, as the hermits are tiny. Are these fish caught with cyanide?